Thermal stability of the prototypical Mn porphyrin-based superoxide dismutase mimic and potent oxidative-stress redox modulator Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride, MnTE-2-PyP5+

Abstract

Cationic Mn porphyrins are among the most potent catalytic antioxidants and/or cellular redox modulators. Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin chloride (MnTE-2-PyPCl5) is the Mn porphyrin most studied in vivo and has successfully rescued animal models of a variety of oxidative stress-related diseases. The stability of an authentic MnTE-2-PyPCl5 sample was investigated hereon by thermogravimetric, derivative thermogravimetric, and differential thermal analyses (TG/DTG/DTA), under dynamic air, followed by studies at selected temperatures to evaluate the decomposition path and appropriate conditions for storage and handling of these materials. All residues were analyzed by thin-layer chromatography (TLC) and UV-vis spectroscopy. Three thermal processes were observed by TG/DTG. The first event (endothermic) corresponded to dehydration, and did not alter the MnTE-2-PyPCl5 moiety. The second event (endothermic) corresponded to the loss of EtCl (dealkylation), which was characterized by gas chromatography-mass spectrometry. The residue at 279 °C had UV-vis and TLC data consistent with those of the authentic, completely dealkylated analogue, MnT-2-PyPCl. The final, multi-step event corresponded to the loss of the remaining organic matter to yield Mn3O4 which was characterized by IR spectroscopy. Isothermal treatment at 188 °C under static air for 3 h yielded a mixture of partially dealkylated MnPs and traces of the free-base, dealkylated ligand, H2T-2-PyP, which reveals that dealkylation is accompanied by thermal demetallation under static air conditions. Dealkylation was not observed if the sample was heated as a solid or in aqueous solution up to ∼100 °C. Whereas moderate heating changes sample composition by loss of H2O, the dehydrated sample is indistinguishable from the original sample upon dissolution in water, which indicates that catalytic activity (on Mn basis) remains unaltered. Evidently, dealkylation at high temperature compromises sample activity.

Transformation of Metal‐Organic Frameworks into Stable Organic Frameworks with Inherited Skeletons and Catalytic Properties

“…In the high-resolution Cu2p XPS spectra, the absence of Cu2p 3/2 peaks for metallic Cu (932.7 eV) and Cu 2 O( 932.5 eV) further proved sufficient etching of the metallic Cu and Cu 2 Os pecies. [13] As expected, the pyrrolic nitrogen became the predominant species at 800 8 8C, along with an ew peak at 398.4 eV that belongs to the pyridinic nitrogen. [12] Thea bsence of the Cu2p 3/2 peak at 935.2 eV in the XPS of CZJ-6-800B indicates that Cu II -porphyrin was completely carbonated at 800 8 8C.…”

Sodium Copper Chlorophyllin Immobilization onto Hippospongia communis Marine Demosponge Skeleton and Its Antibacterial Activity

“…As shown in Figure 8a, the thermogram of SCC contains three discrete characteristic decomposition steps. The first weight loss, of about 4%, between 85 and 115 °C can simply be ascribed to the escape of moisture or air adsorbed in the sample [57]. According to [51], the second decomposition step, in the temperature range 240–370 °C, with a percentage loss of 20%, may be attributed to the elimination of Cu 2+ ions.…”

The copper chelator ATN-224 induces peroxynitrite-dependent cell death in hematological malignancies

“…MnTBAP 3− was synthesized, purified and analyzed by several methods, including LCMS as described [15, 16]. The purity and stability of both compounds were addressed by the studies of Reboucas et al [16, 17]. FeTM-4-PyP 5+ , which exists as a monohydroxo species (OH)FeTM-4-PyP 4+ at pH 7.8 [14], was purchased from Cayman (Ann Arbor, MI).…”